program Treug;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var x1,x2,x3,y1,y2,y3,S:integer;

begin
readln (x1,y1,x2,y2,x3,y3);
s:=x1*y2-x2*y1+x2*y3-x3*y2+x3*y1-x1*y3;
writeln('2s=',s);
readln;

end.
